This invention relates to a method and apparatus for taking samples from or administering medication to a patient, and, in a preferred form, for the continuous monitoring of a given physiological condition of an ambulatory patient.
One form of the invention is concerned simply with taking a sample from a patient without the presence of a qualified attendant, for example at a given hour of the night. A more developed form of the invention is concerned with continuous monitoring.
The continuous monitoring of certain physiological parameters in patients who are going about their normal lives has been an important advance in diagnostics over the last fifteen years. Knowledge of the effect of the stresses of actual living on for example the patient's ECG or EEG has added greatly to the clinician's capacity to understand the patient's illness and prescribe appropriate drugs.
However, it has not been possible for the clinician to follow the concentration of these drugs in the patient's blood, and relate it in detail to the changes produced in for example heart or brain action. To date, there has been no effective means of withdrawing on a regular basis a plurality of discrete samples of blood from the ambulatory patient.
Hitherto efforts have been made to draw off a sample of blood continuously, either for testing continuously or for separation into aliquots for testing. However, trouble arises over blocking of the cannula by blood clots, and the simultaneous administration of an anticoagulant has not proved feasible at the low flow rates required for an ambulatory device.
The same problems arise if it is required to take a single sample at a given time when no attendance can be provided.